Mixing of gasolines and additives to achieve various octanes ratings for different spark ignition engines has been taking place for decades. Determinations of performance or octane ratings of fuels are normally carried out on the basis of comparative tests against certified reference fuels of known and controlled characteristics. Conversely, the determination of octane requirements of engines and vehicles, are again carried out by repetitive testing with a range of reference test fuels of known characteristics.
These reference tests fuels are normally pre-mixed in precise ratios to yield specific performance or octane ratings in accordance with blend ratio tables issued by the test fuel producers.
Blended fuels are then stored and introduced to the laboratory engine or vehicle in separate containers. While these widely adopted practices do not compromise the performance of these tests in laboratories or ground vehicle settings, the storage of a wide range of test fuels in a test aircraft raises serious installation and safety issues.
To perform fuel evaluations and octane determination tests on ground and aircraft in-flight settings in a safe and expeditious manner, the test fuels blender system of the present invention has been developed.
The system is an on-board and in-line system for blending two fuels of known characteristics to achieve instantaneous in-line change in the octane rating of fuel flowing to the engine. The fuel blending system may be used in conjunction with a detonation indication system set forth in applicant's pending application, Serial No. 346,822, titled Aircraft Engine Detonation Indication System: The blending system of the present invention is utilized in determining the octane sensitivity factors of unleaded fuels and engine octane requirements. The blending system provides a means of precise in-line blending of two reference fuels in an on-board aircraft or land vehicle installation. Based on appropriate calibration blending curves, the system will provide instantaneous indications of both lean and rich performance ratings of the fuel. Instantaneous lean and rich performance ratings of the blended fuel stream may be recorded concurrently with engine parameters and ambient test data, and with combustion knock severity numbers derived from the previously mentioned detonation indication system.